Tenants use about 30% more water and do not generally report leaks.Take 60% of gross rents for a D area with higher evictions and make readies and collection efforts with increased bookkeeping.75,600 X .40 ( 60% costs) = 29,240 NOI29,240 at a 10 cap is a value at 292,400 ( This is optimistic as D areas trade for 12 caps usually).175,000 purchase plus  estimate likely 13k to 14k a unit rehab so about 196,000.

Do ask for a proof of funds?

Collect some data points over the course of a month or so and base an argument on that. 

Many banks will require at CAP EX set aside of $300 per door per year.Keep in mind if you are paying for a management compay to manage the property of this size it will be close to 10% of gross rent collections.  

If they can't provide proper proof of income, or if they have more family members than your municipality allows in your apartment, or if they are felons, sexual predators, or other classes that your locale allows you to restrict applications based on, then good.  

Thoughts on these type of tenants and collecting rent this way?

Three different business modelsPurchasing notes at a discount requires sourcing notes, analyzing notes, negotiating price, and raising the capital to fund the purchaseBrokering notes is an intermediary function which requires sourcing notes, sourcing buyers, and connecting the two by best fitFactoring is the purchase of receivables and requires sourcing businesses with receivables and cash flow problems, analyzing the receivables, negotiating terms, and raising capital for the purchase of receivables, and collecting on the receivables.In actuality, factoring is the highest risk highest return.  

Unless they are doing something far and away from collection of rent, depositing, preparing monthly statements, then 10% seems equitable.

Personally it is frustrating that the animal does not have to be trained or proof that it is trained to deal with the disability given.  

All my realtor wants is proof of funds.